In the single-center phase III MIRAGE trial reported in JAMA Oncology, Amar U. Kishan, MD, and colleagues found that use of margin reduction with magnetic resonance imaging (MRI)-guided stereotactic body radiotherapy (SBRT) resulted in significantly reduced acute genitourinary (GU) and gastrointestinal (GI) toxicity vs computed tomography (CT)-guided SBRT in patients with localized prostate adenocarcinoma.
Amar U. Kishan, MD
Study Details
In the open-label trial, 156 patients at the University of California, Los Angeles were randomly assigned between May 2020 and October 2021 to receive MRI-guided (n = 79) or CT-guided (n = 77) SBRT. Planning margins of 2 mm in the MRI group and 4 mm in the CT group were used to deliver 40 Gy in five fractions. The primary endpoint was acute (≤ 90 days from SBRT) grade ≥ 2 GU toxicity; acute grade ≥ 2 GI toxicity was a secondary endpoint.
Key Findings
A prespecified interim futility analysis conducted after 100 patients reached ≥ 90 days after SBRT was performed in October 2021, with the sample size being re-estimated and the trial closed to accrual early. All patients had ≥ 3 months of follow-up.
Grade ≥ 2 acute GU toxicity occurred in 24.4% (95% confidence interval [CI] = 15.4%–35.4%) of the MRI-guided group vs 43.4% (95% CI = 32.1%–55.3%) of the CT-guided group (P = .01). Grade ≥ 2 acute GI toxicity occurred in 0.0% (95% CI = 0.0%–4.6%) of the MRI-guided group vs 10.5% (95% CI = 4.7%–19.7%) of the CT-guided group (P = .003).
A ≥ 15-point increase in patient-reported International Prostate Symptom Score (IPSS) at 1 month was observed in 5 (6.8%) of 72 patients in the MRI-guided group vs 14 (19.4%) of 74 in the CT-guided group (P = .01). A clinically significant (≥ 12-point) decrease in patient-reported Expanded Prostate Cancer Index Composite-26 (EPIC-26) bowel score at 1 month was observed in 17 (25.0%) of 68 patients in the MRI-guided group vs 34 (50.0%) of 68 in the CT-guided group (P = .001).
The investigators concluded, “In this randomized clinical trial, compared with CT-guidance, MRI-guided SBRT significantly reduced both moderate acute physician-scored toxic effects and decrements in patient-reported quality of life. Longer-term follow-up will confirm whether these notable benefits persist.”
Dr. Kishan, of the University of California, Los Angeles, is the corresponding author for the JAMA Oncology article.
Disclosure: The study was supported by the U.S. Department of Defense, American Society for Radiation Oncology, Prostate Cancer Foundation, and others. For full disclosures of the study authors, visit jamanetwork.com.
